3970010 1970 blocks: Where were they cast?

[Dan P.]

Were all 1970 3970010 blocks cast in the same foundry? Flint? Saginaw?

If cast in multiple foundries, then which ones and how can these blocks be differentiated? Thanks!

[Joe L.]

Re: 3970010 1970 blocks: Where were they cast?

Were all 1970 3970010 blocks cast in the same foundry? Flint? Saginaw?

If cast in multiple foundries, then which ones and how can these blocks be differentiated? Thanks!

Dan-----

All of the 3970010 blocks used in Corvettes were cast at the Saginaw Grey Iron Foundry. They were machined and assembled at Flint which is about 65 miles from Saginaw.

The 3970010 blocks may also have been cast at Tonawanda, but none of these were used in Corvettes.

A Saginaw-cast and Flint-machined block regardless of casting number is most easily identified by the presence of a 1/8" NPT square head pipe plug located on front of the passenger side of the block, just above the timing cover. If it has this plug, it's a Saginaw-cast and Flint machined/assembled block.

A Tonawanda-cast block will not have the plug, regardless of casting number. It will also have a large "T" cast on the bellhousing flange and/or above the oil filter.

Some 3970010 blocks may also have been cast at St. Catherines, Canada. I've forgotten whether these have the aforementioned plug, or not. However, these blocks will have a large "K" on the bellhousing flange and/or above the oil filter.

[R N.]

Re: 3970010 1970 blocks: Where were they cast?

Dan-----

All of the 3970010 blocks used in Corvettes were cast at the Saginaw Grey Iron Foundry. They were machined and assembled at Flint which is about 65 miles from Saginaw.

The 3970010 blocks may also have been cast at Tonawanda, but none of these were used in Corvettes.

A Saginaw-cast and Flint-machined block regardless of casting number is most easily identified by the presence of a 1/8" NPT square head pipe plug located on front of the passenger side of the block, just above the timing cover. If it has this plug, it's a Saginaw-cast and Flint machined/assembled block.

A Tonawanda-cast block will not have the plug, regardless of casting number. It will also have a large "T" cast on the bellhousing flange and/or above the oil filter.

Some 3970010 blocks may also have been cast at St. Catherines, Canada. I've forgotten whether these have the aforementioned plug, or not. However, these blocks will have a large "K" on the bellhousing flange and/or above the oil filter.

Hi Joe,

What was that plug for?

[Clem Z.]

Re: 3970010 1970 blocks: Where were they cast?

Hi Joe,

What was that plug for?

it went into the main oil gallery and i would guess it was a oil feed for a air compressor for air brakes on trucks. the tall block 366/427 had the same feature and it was for the air compressor

[Joe L.]

Re: 3970010 1970 blocks: Where were they cast?

it went into the main oil gallery and i would guess it was a oil feed for a air compressor for air brakes on trucks. the tall block 366/427 had the same feature and it was for the air compressor

clem and Kurt-----


In addition, I believe the machining equipment used at Flint and Tonawanda differed. At Flint, the equipment required that a drilling be made at the location of the plug in order to connect other internal oil galleries. After the drilling was made, it had to be capped with a plug.

Tonawanda was able to accomplish the connecting of the oil galleries without the need for this external drilling. How they did this is a total mystery to me, though.

[Michael W.]

Re: 3970010 1970 blocks: Where were they cast?

Some 3970010 blocks may also have been cast at St. Catherines, Canada. I've forgotten whether these have the aforementioned plug, or not. However, these blocks will have a large "K" on the bellhousing flange and/or above the oil filter.

I have a 0010 block cast by McKinnon, it does not have the plug.

[Joe L.]

Re: 3970010 1970 blocks: Where were they cast?

I have a 0010 block cast by McKinnon, it does not have the plug.

Mike-----


Excellent information. It appears that McKinnon "took after" Tonawanda. In fact, I believe that some McKinnon-cast blocks may have actually been machined/assembled at Tonawanda. Of course, none would have been used in Corvettes.

Your block does have the large "K" cast on the bellhousing flange and/or above the oil filter, doesn't it?

[Jack H.]

Re: 3970010 1970 blocks: Where were they cast?

I believe that's incorrect...

The application where I've seen the front oil hole used (the one that's plugged in Corvette applications) is in truck and coach applications where you had a 'cab forward/cab over' body that positioned the driver and instrument cluster directly forward and above the engine.

My hunch is since Saginaw/Flint was located CLOSE to GMC in Pontiac (compared to Tonawanda), they were the prime supplier of V8 engines and it was simpler to drill & tap all V8's for the 'truck' application and simply plug the hole for passenger car engines...

[Clem Z.]

Re: 3970010 1970 blocks: Where were they cast?

I believe that's incorrect...

The application where I've seen the front oil hole used (the one that's plugged in Corvette applications) is in truck and coach applications where you had a 'cab forward/cab over' body that positioned the driver and instrument cluster directly forward and above the engine.

My hunch is since Saginaw/Flint was located CLOSE to GMC in Pontiac (compared to Tonawanda), they were the prime supplier of V8 engines and it was simpler to drill & tap all V8's for the 'truck' application and simply plug the hole for passenger car engines...

could be because on the BBC the hole was where the air compressor oil feed was taken from on larger trucks. when we converted SBC to dry sump lubrication we drilled that hole to 7/16" and tapped it to feed the oil directly into the main oil gallery to eliminate all the 90 degree corners in the original oiling system

[Michael W.]

Re: 3970010 1970 blocks: Where were they cast?

Mike-----

Your block does have the large "K" cast on the bellhousing flange and/or above the oil filter, doesn't it?

Excuse the delay, haven't been in the garage for several days. I looked in front, above and all around the oil filter mounting boss but found no indication of a cast K on the block. Any other places to look?

[Tom P.]

Re: 3970010 1970 blocks: Where were they cast?

And some additional info (which REALLY surprises me that NCRS fanatics haven't mentioned yet!!!).
If the block is a Tonawanda casting, the CAST date on the bell housing flange will end with TWO digits for the year. For example: B2569 would translate to Feb 25, 1969. But, if it was a Flint block (Saginaw casting), the cast date would be B259. The Flint casting dates only have ONE digit for the year. Sooooooooooo, how do you know if the block is a 59, 69, 79, etc??? Well, first you have to know what block you're dealing with. For example, there were no 1969 or 1979 283 engines. Thus, if the block is a 283, and the casting date is XXX9, then you automatically KNOW that it is a 1959 283. Same with a 327. There were NO 327s in 59 or 79. There were no 350 in 59, but there WERE 350s in 69 and 79. A 69 350 will have a LEFT side dipstick and a 79 350 will have a RIGHT side dipstick. So, you first need to understand what general era of engine you're looking at.

And then there's the issue of the hole/plug (or lack of) in the front of the block.
ALLLLLLLLLLLLLLLLL SB blocks have the boss cast for this hole. When the hole/plug is present in a block, it is simply a drilled/tapped (1/8in pipe threads) passage from the front of the block down into the top-center oil galley. Nothing special. I've drilled many of the blocks that did not have this passage drilled. Makes and EXCELLENT location to mount a direct oil pressure gauge.
Now, as to the why this passage was ORIGINALLY in SB blocks.
In the beginning (1955) all 265 engines had this passage drilled/tapped. Why? Because this was the source of oil for the OPTIONAL oil filter on cars/trucks (no oil filter option was available for 1955 V8 Vettes). The 1955 optional oil filter was a canister, with a mounting bracket, which was attached BETWEEN the intake manifold and the thermostat housing. Oil came up from the center oil galley, up through that passage in the front of the block, through a hose that fed oil into the filter canister. Then, the return oil (again, 1955 only) went through a hose from the canister to a drilled/tapped hole on the right side of the intake manifold beside the carb base. ONLY 1955 V8 intake manifolds have this drilled/tapped hole (and plugged on cars without a filter). OK, so you say what about the 55 engines that DID NOT come from the factory with the optional oil filter? LOTS of 55 Chevys were built without an oil filter, and it was REAL COMMON for dealers to install a filter BEFORE delivery to the customer. And, with that thought, how do you tell the difference between a factory installed oil filter and a dealer installed oil filter on a 55 V8?? Factory canister was black, dealer installed filter was blue with an orange lid (or was it the other way around? You guess). And since 1955, all SB blocks have had this boss which can be drilled (and is drilled on Flint blocks) and tapped.

Soooooooooooooooo, what do you say when you run across a Tonawanda block with the drilled/tapped hole in the front of the block? You say Tom Parsons did that!

[Joe L.]

Re: 3970010 1970 blocks: Where were they cast?

Excuse the delay, haven't been in the garage for several days. I looked in front, above and all around the oil filter mounting boss but found no indication of a cast K on the block. Any other places to look?

Mike----


Did you look on the bellhousing flange near either the casting number or casting date?

[David L.]

Re: 3970010 1970 blocks: Where were they cast?

Excuse the delay, haven't been in the garage for several days. I looked in front, above and all around the oil filter mounting boss but found no indication of a cast K on the block. Any other places to look?

I have seen several 1970 "010" McKinnon blocks with a large letter "M" casting inside a box. The stamped number on the front "pad" starts with the letter "K". These blocks were in low horsepower 1970 Chevrolets.

[Wayne L.]

Re: 3970010 1970 blocks: Where were they cast?

Dan-if you still have questions, give me a call. I've seen several McKinnon blocks as well as the Tonawanda and Saginaw blocks.

[Joe L.]

Re: 3970010 1970 blocks: Where were they cast?

I have seen several 1970 "010" McKinnon blocks with a large letter "M" casting inside a box. The stamped number on the front "pad" starts with the letter "K". These blocks were in low horsepower 1970 Chevrolets.

David----

I guess McKinnon used both "K" and "M" casting identifiers. I don't ever recall seeing an "M" but I've definitely seen "K". I thought the "M" might be used by the GM foundry in Toluca, Mexico. The assembly plant there definitely uses an "M" prefix code on stampings.